可见光移相点衍射干涉仪的空气扰动误差分析

Analysis of air turbulence errors for visible light phase shifting point diffraction interferometer

为了提高可见光移相点衍射干涉仪的测量精度， 对空气扰动误差的分析以及有效的抑制是十分必要的。 利用自行设计的十三步移相算法与传统的五步移相算法对空气扰动误差进行了理论分析与仿真计算，分析结果证明了新算法的优越性，并且通过对干涉仪的空气扰动误差的分析，最终得到了干涉仪工作的环境控制条件， 如果采用十三步移相算法， 保证空气温度变化控制在±0.005 ℃以内，压强变化控制在±1 Pa 以内，水汽压变化控制在±5 Pa 以内，温度梯度变化控制在 0~0.01 ℃范围内，压强梯度变化控制在 0~2 Pa 范围内，最后再对多次测量结果取平均，则空气扰动误差引起的位相误差将在测量精度允许的范围内。 在现有的实验条件下搭建了原理实验装置，实验结果表明：十三步算法和五步算法的结果相近，但十三步算法的重复性优于五步算法。 采用十三步算法，在所构建的实验装置上实现了 RMS 值优于 λ/10 000（λ=632.8 nm）的检测重复性。

In order to increase the measuring accuracy of the visible light phase-shifting point diffraction interferometer, it is important to analyze and effectively restrain the air turbulence errors. The air turbulence errors were analyzed and simulated by the 5-step and 13-step phase-shifting algorithm which was designed by the author. The results indicated the superiority of the new algorithm. Through the analysis of the air turbulence errors, the conditions of the environmental control of the interferometer were obtained. When the 13-step algorithm was utilized, the variational range of air temperature was controlled within ±0.005 ℃, air pressure within ±1 Pa, air vapor pressure within ±5 Pa, temperature gradient within 0-0.01 ℃, pressure gradient within 0-2 Pa. At last, the measured results were averaged, the phase error caused by the air turbulence errors was in the permitting range of the measuring accuracy. Theexperimental facility was built according to the experimental conditions. The experimental results show that the results of the 5-frame algorithm and the 13-frame algorithm are approximate, but the repeatability of the 13-frame algorithm is better than that of the 5-frame algorithm. When the 13- frame algorithm is adopted, the measuring repeatability （RMS） of the experimental facility is better than λ/10 000（λ=632.8 nm）.